Semiconductor device

ABSTRACT

A capacitive component region is formed below a temperature detecting diode or below a protective diode. In addition, the capacitive component region is formed below an anode metal wiring line connecting the temperature detecting diode and an anode electrode pad and below a cathode metal wiring line connecting the temperature detecting diode and a cathode electrode pad. The capacitive component region is an insulating film interposed between polysilicon layers. Specifically, a first insulating film, a polysilicon conductive layer, and a second insulating film are sequentially formed on a first main surface of a semiconductor substrate, and the temperature detecting diode, the protective diode, the anode metal wiring line, or the cathode metal wiring line is formed on the upper surface of the second insulating film. Therefore, it is possible to improve the static electricity resistance of the temperature detecting diode or the protective diode.

This application is a divisional of U.S. application Ser. No. 14/485,554filed on Sep. 12, 2014, and allowed on Jun. 3, 2016, which was acontinuation under 35 U.S.C. 120 of International ApplicationPCT/JP2013/067575 having the International Filing Date of Jun. 26, 2013,and having the benefit of the earlier filing date of JapaneseApplication No. 2012-177381, filed on Aug. 9, 2012. All of theidentified applications are fully incorporated herein by reference.

TECHNICAL FIELD

The invention relates to a semiconductor device including a MOSsemiconductor element and a temperature detecting diode or a protectivediode and a method for producing the same.

BACKGROUND ART

In the related art, a semiconductor device has been known which includesa diode as an overheat protection function in order to prevent thethermal breakdown of a MOS (metal-oxide film-semiconductor insulatedgate) semiconductor element, such as a metal oxide semiconductor fieldeffect transistor (MOSFET) or an insulated gate bipolar transistor(IGBT). Specifically, in order to protect the MOS semiconductor elementfrom overvoltage, a plurality of diodes or bidirectional diodes areprovided between the gate and the source or between the gate and thedrain.

As the MOS semiconductor device according to the related art whichincludes the temperature detecting diode, a device has been proposed inwhich a capacitor is formed so as to overlap a temperature detectingdiode in the thickness direction of a semiconductor substrate and iselectrically connected in parallel to the temperature detecting diode,in order to reduce radio frequency noise acting on the temperaturedetecting diode (for example, see the following Patent Document 1).

Another MOS semiconductor device has been proposed in which a protectivecapacitor or a diode and a temperature detecting diode are formed on thesame substrate and the protective capacitor or the diode is connected inparallel to the temperature detecting diode, in order to improve thestatic electricity resistance of the temperature detecting diode (forexample, see the following Patent Document 2 and Patent Document 3).

Another MOS semiconductor device has been proposed which includes acapacitor for preventing a change in characteristics or damage when avoltage that is higher than the breakdown voltage of a protective diodefor a temperature detecting diode is applied to the protective diode inthe reverse direction due to, for example, electrostatic discharge (forexample, see the following Patent Document 4).

Another MOS semiconductor device has been proposed in which, in order toprevent the arrangement position of a temperature detecting diode frombeing limited by a diffusion structure in a portion below thetemperature detecting diode (a portion which is closer to asemiconductor substrate than the temperature detecting diode), aninsulating film is formed on the semiconductor substrate, a conductivelayer is formed on the insulating film, the temperature detecting diodeis formed on the conductive layer, with an insulating film interposedtherebetween, and the temperature detecting diode is electricallyinsulated from the semiconductor substrate (for example, see thefollowing Patent Document 5).

As another MOS semiconductor device, a device has been proposed in whichtwo polysilicon diodes having an insulating film interposed therebetweenare formed on an insulating film formed on the main surface of asemiconductor substrate main surface and the insulating film between thepolysilicon diodes is used as a capacitive component region (forexample, see the following Patent Document 6). In the following PatentDocument 6, the insulating film serving as a capacitor has an openingportion and the polysilicon diode on the insulating film and thepolysilicon diode below the insulating film are connected to each otherthrough the opening portion. As such, since the two-layer polysilicondiodes are formed, the area of the polysilicon diode is reduced and thecapacitor is electrically insulated from the semiconductor substrate.Therefore, stable capacitance is obtained.

As another MOS semiconductor device, a device has been proposed in whicha plurality of stripe-shaped or rectangular zener diodes are formed in agate pad and are electrically connected in parallel to each other,thereby improving static electricity resistance (for example, see thefollowing Patent Document 7). In addition, as a method for producing aMOS semiconductor device, a production method has been proposed inwhich, in order to reduce the number of steps when a polysilicon diode,a capacitor, a resistor, and an insulated gate semiconductor element areformed on the same semiconductor substrate, a gate oxide film and anoxide film thicker than the gate oxide film are formed, a polysiliconlayer is formed thereon and is then patterned to form a gate electrode,the diode, the capacitor, and the resistor (for example, see thefollowing Patent Document 8).

As another method for producing a MOS semiconductor device, a method hasbeen proposed in which an insulating film between a temperaturedetecting diode and a semiconductor substrate and a gate oxide film areformed in the same step (for example, see the following Patent Document9).

CITATION LIST Patent Document

Patent Document 1: JP 4329829 B1

Patent Document 2: JP 7-202224 A

Patent Document 3: JP 4765252 B1

Patent Document 4: JP 2007-335474 A

Patent Document 5: JP 2005-26279 A

Patent Document 6: JP 6-45620 A

Patent Document 7: JP 2009-43953 A

Patent Document 8: JP 3413569 B1

Patent Document 9: JP 2010-129707 A

In the MOS semiconductor device according to the related art, asillustrated in FIG. 20, a temperature detecting diode 1 is arranged inthe vicinity of a central portion in which the temperature of the MOSsemiconductor device is at the highest. FIG. 20 is a plan viewillustrating the structure of the MOS semiconductor device according tothe related art. FIG. 21 is a cross-sectional view illustrating thecross-sectional structure taken along the cutting line A-A′ of FIG. 20.As illustrated in FIG. 21, the temperature detecting diode 1, an anodeelectrode pad 3 and a cathode electrode pad 4 are formed on aninsulating film 19 that is thicker than a gate insulating film 32. Ananode metal wiring line 6 that connects the temperature detecting diode1 and the anode electrode pad 3 or a cathode metal wiring line 7 thatconnects the temperature detecting diode 1 and the cathode electrode pad4 is also formed on the insulating film 19. The structure portion of theMOS semiconductor device is formed on the insulating film 19 in order toprevent the breakdown of the temperature detecting diode 1 or protectivediodes 21 and 22 due to static electricity or overvoltage applied to agate electrode pad 5, a source electrode 34, an anode electrode, or acathode electrode.

However, the temperature detecting diode 1 or the protective diodes 21and 22 have low static electricity resistance. For example, a method ofconnecting a resistor with high resistance which forms a protectivediode for the temperature detecting diode 1 has been used in order toimprove the static electricity resistance of the temperature detectingdiode 1. However, when a large diode is formed in order to protect thetemperature detecting diode 1, a leakage current increases,on-resistance (on-voltage) increases due to an increase in invalid area,or an element area (the area of an active region 8) increases, whichresults in an increase in costs.

The protective diode 21 which is formed between the gate electrode 33and the source electrode 34 of the MOS semiconductor element or theprotective diode 22 which is formed between the gate electrode 33 andthe drain electrode 35 of the MOS semiconductor element are formed alongthe gate electrode pad 5. Therefore, the pn junction area of theprotective diodes 21 and 22 needs to increase in order to increase thecapacitance of the protective diode 21 and 22, which results in anincrease in the area of the protective diodes 21 and 22. Therefore, thearea of the active region 8 is reduced and on-resistance increases.

The invention has been made in order to solve the above-mentionedproblems of the related art and an object of the invention is to providea semiconductor device capable of improving the static electricityresistance of a temperature detecting diode or a protective diode and amethod for producing the same.

SUMMARY

In order to solve the above-mentioned problems and achieve the object ofthe invention, a semiconductor device according to an aspect of theinvention includes a semiconductor element that makes a current flow ina thickness direction of a semiconductor substrate and a diode that isconnected to the semiconductor element. The semiconductor device has thefollowing characteristics. A first insulating film is formed on a firstmain surface of the semiconductor substrate. A conductive layer isformed on the first insulating film. A second insulating film is formedon the conductive layer. The diode including a first-conductivity-typelayer and a second-conductivity-type layer formed on the secondinsulating film is formed. A first capacitor that has the secondinsulating film between the first-conductivity-type layer and theconductive layer as a first capacitive component region is formed. Asecond capacitor that has the second insulating film between thesecond-conductivity-type layer and the conductive layer as a secondcapacitive component region is formed. The conductive layer iselectrically insulated.

The semiconductor device according to the above-mentioned aspect of theinvention may further have the following characteristics. Thesemiconductor element further may have the following structure. A firstsemiconductor layer of a first conductivity type is formed in a surfacelayer of the first main surface of the semiconductor substrate. A firstsemiconductor region of a second conductivity type is selectively formedin a surface layer of the first semiconductor layer which is close tothe first main surface. A second semiconductor region of the firstconductivity type is selectively formed in a surface layer of the firstsemiconductor region which is close to the first main surface. A gateelectrode is formed on a surface of the first semiconductor region, witha gate insulating film interposed therebetween, in a portion which isinterposed between the first semiconductor layer and the secondsemiconductor region.

The semiconductor device according to the above-mentioned aspect of theinvention may further include a third capacitor that has the firstinsulating film between the conductive layer and the semiconductorsubstrate as a third capacitive component region.

The semiconductor device according to the above-mentioned aspect of theinvention may further have the following characteristics. The conductivelayer is divided into a first conductive layer portion that faces thefirst-conductivity-type layer, with the second insulating filminterposed therebetween, and a second conductive layer portion thatfaces the second-conductivity-type layer, with the second insulatingfilm interposed therebetween. A space between the first conductive layerportion and the second conductive layer portion is filled with thesecond insulating film. A third capacitor that has the second insulatingfilm provided between the first conductive layer portion and the secondconductive layer portion as a third capacitive component region isformed.

The semiconductor device according to the above-mentioned aspect of theinvention may further have the following characteristics. A fourthcapacitor that has the first insulating film between the firstconductive layer portion and the semiconductor substrate as a fourthcapacitive component region is formed. A fifth capacitor that has thefirst insulating film between the second conductive layer portion andthe semiconductor substrate as a fifth capacitive component region isformed.

In order to solve the above-mentioned problems and achieve the object ofthe invention, a semiconductor device according to another aspect of theinvention includes a semiconductor element that makes a current flow ina thickness direction of a semiconductor substrate and a temperaturedetecting diode that detects a temperature of the semiconductor element.The semiconductor device has the following characteristics. Thetemperature detecting diode is provided in an active region of thesemiconductor element. An anode metal wiring line that is connected toan anode of the temperature detecting diode is provided on a first mainsurface side of the semiconductor substrate. A cathode metal wiring linethat is connected to a cathode of the temperature detecting diode isprovided on the first main surface side of the semiconductor substrate.A first insulating film is formed on a first main surface of thesemiconductor substrate between the anode and cathode metal wiring linesand the semiconductor substrate. A conductive layer is formed on thefirst insulating film. A second insulating film is formed on theconductive layer. A first semiconductor layer that is connected to theanode metal wiring line is formed between the second insulating film andthe anode metal wiring line. A second semiconductor layer that isconnected to the cathode metal wiring line is formed between the secondinsulating film and the cathode metal wiring line. A first capacitorthat has the second insulating film between the first semiconductorlayer and the conductive layer as a first capacitive component region isformed. A second capacitor that has the second insulating film betweenthe second semiconductor layer and the conductive layer as a secondcapacitive component region is formed. The conductive layer iselectrically insulated.

The semiconductor device according to the above-mentioned aspect of theinvention may further have the following characteristics. Thesemiconductor element may have the following structure. A firstsemiconductor layer of a first conductivity type is formed in a surfacelayer of the first main surface of the semiconductor substrate. A firstsemiconductor region of a second conductivity type is selectively formedin a surface layer of the first semiconductor layer which is close tothe first main surface. A second semiconductor region of the firstconductivity type is selectively formed in a surface layer of the firstsemiconductor region which is close to the first main surface. A gateelectrode is formed on a surface of the first semiconductor region, witha gate insulating film interposed therebetween, in a portion which isinterposed between the first semiconductor layer and the secondsemiconductor region.

The semiconductor device according to the above-mentioned aspect of theinvention may further include a third capacitor that has the firstinsulating film between the conductive layer and the semiconductorsubstrate as a third capacitive component region.

The semiconductor device according to the above-mentioned aspect of theinvention may further have the following structure. The conductive layeris divided into a first conductive layer portion that faces the firstsemiconductor layer, with the second insulating film interposedtherebetween, and a second conductive layer portion that faces thesecond semiconductor layer, with the second insulating film interposedtherebetween. A space between the first conductive layer portion and thesecond conductive layer portion is filled with the second insulatingfilm. A third capacitor that has the second insulating film providedbetween the first conductive layer portion and the second conductivelayer portion as a third capacitive component region is formed.

The semiconductor device according to the above-mentioned aspect of theinvention may further have the following structure. A fourth capacitorthat has the first insulating film between the first conductive layerportion and the semiconductor substrate as a fourth capacitive componentregion is formed. A fifth capacitor that has the first insulating filmbetween the second conductive layer portion and the semiconductorsubstrate as a fifth capacitive component region is formed.

In the semiconductor device according to the above-mentioned aspect ofthe invention, the diode may be a temperature detecting diode that isprovided in an active region of the semiconductor element and detects atemperature of the semiconductor element.

The semiconductor device according to the above-mentioned aspect of theinvention may further include a gate electrode pad that is connected tothe gate electrode and a source electrode that is connected to the firstsemiconductor region and the second semiconductor region. The diode maybe a protective diode that is formed between the gate electrode pad andthe source electrode.

The semiconductor device according to the above-mentioned aspect of theinvention may further include a gate electrode pad that is connected tothe gate electrode, a third semiconductor region of the firstconductivity type that is selectively formed in the surface layer of thefirst semiconductor layer which is close to the first main surface, anda drain electrode that is connected to the third semiconductor region.The diode may be a protective diode that is formed between the gateelectrode pad and the drain electrode.

In order to solve the above-mentioned problems and achieve the object ofthe invention, a method for producing the semiconductor device accordingto the above-mentioned aspect of the invention has the followingcharacteristics. First, a step of forming the gate insulating film andthe first insulating film on the first semiconductor region isperformed. Then, a step of forming the gate electrode which is made ofpolysilicon on the gate insulating film and forming the conductive layerwhich is made of polysilicon on the first insulating film is performed.Then, a step of patterning the gate electrode and the conductive layeris performed. Then, a step of forming the second insulating film on thepatterned conductive layer is performed. Then, a step of forming asecond semiconductor layer which is made of polysilicon on the secondinsulating film is performed. Then, a step of implantingfirst-conductivity-type impurity ions to selectively form thefirst-conductivity-type layer of the diode in the second semiconductorlayer and forming the second semiconductor region, which will be asource region of the semiconductor element, in the surface layer of thefirst semiconductor region close to the first main surface is performed.

In order to solve the above-mentioned problems and achieve the object ofthe invention, a method for producing the semiconductor device accordingto the above-mentioned aspect of the invention has the followingcharacteristics. First, a step of forming the gate insulating film andthe first insulating film on the first semiconductor region isperformed. Then, a step of forming the gate electrode which is made ofpolysilicon on the gate insulating film and forming the conductive layerwhich is made of polysilicon on the first insulating film is performed.Then, a step of patterning the gate electrode and the conductive layeris performed. Then, a step of forming the second insulating film on thepatterned conductive layer is performed. Then, a step of forming thefirst semiconductor layer which is made of polysilicon on the secondinsulating film so as to be close to the anode metal wiring line andforming the second semiconductor layer which is made of polysilicon onthe second insulating film so as to be close to the cathode metal wiringline is performed.

In order to solve the above-mentioned problems and achieve the object ofthe invention, a semiconductor device according to another aspect of theinvention includes an insulated gate semiconductor element that makes acurrent flow in a thickness direction of a semiconductor substrate and adiode that is connected to the insulated gate semiconductor element. Thesemiconductor device has the following characteristics. A firstinsulating film having a thickness that is equal to or greater than athickness of a gate insulating film of the insulated gate semiconductorelement and equal to or less than 1000 Å is formed on a first mainsurface of the semiconductor substrate. The diode including afirst-conductivity-type layer and a second-conductivity-type layer thatare formed on the first insulating film is arranged. A first capacitorthat has the first insulating film between the first-conductivity-typelayer and the semiconductor substrate as a first capacitive componentregion is formed. A second capacitor that has the first insulating filmbetween the second-conductivity-type layer and the semiconductorsubstrate as a second capacitive component region is formed.

The semiconductor device according to the above-mentioned aspect of theinvention may further have the following characteristics. The insulatedgate semiconductor element may have the following structure. A firstsemiconductor layer of a first conductivity type is formed in a surfacelayer of the first main surface of the semiconductor substrate. A firstsemiconductor region of a second conductivity type is selectively formedin a surface layer of the first semiconductor layer which is close tothe first main surface. A second semiconductor region of the firstconductivity type is selectively formed in a surface layer of the firstsemiconductor region. A gate electrode is formed on a surface of thefirst semiconductor region, with the gate insulating film interposedtherebetween, in a portion which is interposed between the firstsemiconductor layer and the second semiconductor region.

In order to solve the above-mentioned problems and achieve the object ofthe invention, a semiconductor device according to another aspect of theinvention includes an insulated gate semiconductor element that makes acurrent flow in a thickness direction of a semiconductor substrate and atemperature detecting diode that detects a temperature of the insulatedgate semiconductor element. The semiconductor device has the followingcharacteristics. The temperature detecting diode is provided in anactive region of the insulated gate semiconductor element. An anodemetal wiring line that is connected to an anode of the temperaturedetecting diode is provided on a first main surface side of thesemiconductor substrate. A cathode metal wiring line that is connectedto a cathode of the temperature detecting diode is provided on the firstmain surface side of the semiconductor substrate. A first insulatingfilm having a thickness that is equal to or greater than a thickness ofa gate insulating film of the insulated gate semiconductor element andequal to or less than 1000 Å is formed on a first main surface of thesemiconductor substrate between the anode and cathode metal wiring linesand the semiconductor substrate. A first semiconductor layer that isconnected to the anode metal wiring line is formed between the firstinsulating film and the anode metal wiring line. A second semiconductorlayer that is connected to the cathode metal wiring line is formedbetween the first insulating film and the cathode metal wiring line. Afirst capacitor that has the first insulating film between the firstsemiconductor layer and the semiconductor substrate as a firstcapacitive component region is formed. A second capacitor that has thefirst insulating film between the second semiconductor layer and thesemiconductor substrate as a second capacitive component region isformed.

The semiconductor device according to the above-mentioned aspect of theinvention may further have the following characteristics. The insulatedgate semiconductor element may have the following structure. A firstsemiconductor layer of a first conductivity type is formed in a surfacelayer of the first main surface of the semiconductor substrate. A firstsemiconductor region of a second conductivity type is selectively formedin a surface layer of the first semiconductor layer which is close tothe first main surface. A second semiconductor region of the firstconductivity type is selectively formed in a surface layer of the firstsemiconductor region which is close to the first main surface. A gateelectrode is formed on a surface of the first semiconductor region, withthe gate insulating film interposed therebetween, in a portion which isinterposed between the first semiconductor layer and the secondsemiconductor region.

In the semiconductor device according to the above-mentioned aspect ofthe invention, the diode may be a temperature detecting diode that isprovided in an active region of the insulated gate semiconductor elementand detects a temperature of the insulated gate semiconductor element.

The semiconductor device according to the above-mentioned aspect of theinvention may further include a gate electrode pad that is connected tothe gate electrode and a source electrode that is connected to the firstsemiconductor region and the second semiconductor region. The diode maybe a protective diode that is formed between the gate electrode pad andthe source electrode.

The semiconductor device according to the above-mentioned aspect of theinvention may further include a gate electrode pad that is connected tothe gate electrode, a third semiconductor region of the firstconductivity type that is selectively formed in the surface layer of thefirst semiconductor layer which is close to the first main surface, anda drain electrode that is connected to the third semiconductor region.The diode may be a protective diode that is formed between the gateelectrode pad and the drain electrode.

In the semiconductor device according to the above-mentioned aspect ofthe invention, the temperature detecting diode may be made ofpolysilicon. In addition, in the semiconductor device according to theabove-mentioned aspect of the invention, the protective diode may bemade of polysilicon.

In the semiconductor device according to the above-mentioned aspect ofthe invention, the conductive layer may be made of polysilicon.

In the semiconductor device according to the above-mentioned aspect ofthe invention, the temperature detecting diode may be a zener diode. Inaddition, in the semiconductor device according to the above-mentionedaspect of the invention, the protective diode may be a zener diode.

In the semiconductor device according to the above-mentioned aspect ofthe invention, the semiconductor element may be a trench-type insulatedgate semiconductor element. In addition, in the semiconductor deviceaccording to the above-mentioned aspect of the invention, the insulatedgate semiconductor element may be a trench-type insulated gatesemiconductor element.

According to the semiconductor device and the semiconductor deviceproduction method of the invention, the capacitive component region isformed below the temperature detecting diode, below the anode metalwiring line connected to the anode electrode of the temperaturedetecting diode, or below the cathode metal wiring line connected to thecathode electrode of the temperature detecting diode. Therefore, it ispossible to improve the static electricity resistance of the temperaturedetecting diode. In addition, according to the semiconductor device andthe semiconductor device production method of the invention, thecapacitive component region is formed below the protective diode.Therefore, it is possible to improve the static electricity resistanceof the protective diode.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating the structure of a semiconductor deviceaccording to Embodiment 1 of the invention;

FIG. 2 is a cross-sectional view illustrating the structure of asemiconductor device according to Embodiment 2 of the invention;

FIG. 3 is a circuit diagram illustrating the circuit structure of thesemiconductor device according to Embodiment 2 of the invention;

FIG. 4 is a cross-sectional view illustrating the structure of thesemiconductor device according to Embodiment 2 of the invention;

FIG. 5 is a diagram illustrating the structure of a semiconductor deviceaccording to Embodiment 3 of the invention;

FIG. 6 is a diagram illustrating the structure of a semiconductor deviceaccording to Embodiment 4 of the invention;

FIG. 7 is a cross-sectional view illustrating the structure of asemiconductor device according to Embodiment 5 of the invention;

FIG. 8 is a cross-sectional view illustrating another example of thestructure of the semiconductor device according to Embodiment 5 of theinvention;

FIG. 9 is a cross-sectional view illustrating the structure of asemiconductor device according to Embodiment 6 of the invention;

FIG. 10 is a cross-sectional view illustrating the structure of thesemiconductor device according to Embodiment 6 of the invention;

FIG. 11 is a diagram illustrating the structure of a semiconductordevice according to Embodiment 7 of the invention;

FIG. 12 is a cross-sectional view illustrating the structure of asemiconductor device according to Embodiment 8 of the invention;

FIG. 13 is a circuit diagram illustrating the circuit structure of thesemiconductor device according to Embodiment 8 of the invention;

FIG. 14 is a cross-sectional view illustrating the structure of thesemiconductor device according to Embodiment 8 of the invention;

FIG. 15 is a diagram illustrating the structure of a semiconductordevice according to Embodiment 9 of the invention;

FIG. 16 is a diagram illustrating the structure of a semiconductordevice according to Embodiment 10 of the invention;

FIG. 17 is a cross-sectional view illustrating the structure of asemiconductor device according to Embodiment 11 of the invention;

FIG. 18 is a cross-sectional view illustrating a method for producing asemiconductor device according to Embodiment 12 of the invention;

FIG. 19 is a cross-sectional view illustrating a method for producing asemiconductor device according to Embodiment 13 of the invention;

FIG. 20 is a plan view illustrating the structure of a MOS semiconductordevice according to the related art; and

FIG. 21 is a cross-sectional view illustrating a cross-sectionalstructure taken along the cutting line A-A′ of FIG. 20.

DETAILED DESCRIPTION

Hereinafter, various non-limiting embodiments of a semiconductor deviceand a method for producing the same according to the invention will bedescribed in detail with reference to the accompanying drawings. In thespecification and the accompanying drawings, in the layers or regionshaving “n” or “p” appended thereto, an electron or a hole means amajority carrier. In addition, symbols “+” and “−” added to n or p meanthat impurity concentration is higher and lower than that of the layerwithout the symbols. In the description of the following embodiment andthe accompanying drawings, the same components are denoted by the samereference numerals and the description thereof will not be repeated.

In each of the following embodiments, a MOSFET (insulated gate fieldeffect transistor) is used as a MOS semiconductor element. However, theMOS semiconductor element is not limited to the MOSFET. For example, aninsulated gate bipolar transistor (IGBT) can be used as the MOSsemiconductor element.

A temperature detecting diode and a protective diode described in theclaims indicate a temperature detecting diode 1 and a protective diode2, respectively.

Embodiment 1

A semiconductor device according to Embodiment 1 of the invention willbe described. FIG. 1 is a diagram illustrating the structure of thesemiconductor device according to Embodiment 1 of the invention. FIG.1(A) is a plan view illustrating the structure of the semiconductordevice according to Embodiment 1 of the invention and FIG. 1(B) is anequivalent circuit diagram illustrating protective diodes 21 and 22illustrated in FIG. 1(a).

As illustrated in FIGS. 1(a) and 1(b), the semiconductor deviceaccording to Embodiment 1 includes a MOSFET 51, a temperature detectingdiode 1, and the protective diodes 21 and 22 (protective diode 2). Thetemperature detecting diode 1 has a function of detecting thetemperature of the MOSFET 51. The protective diode 21 is connectedbetween a gate G and a source S of the MOSFET 51 and has a function ofpreventing dielectric breakdown due to, for example, static electricityor surge (transient overvoltage). The protective diode 22 is connectedbetween the gate G and a drain D of the MOSFET 51 and has a function ofpreventing the breakdown of the element due to, for example, staticelectricity or surge.

The temperature detecting diode 1 is formed in the vicinity of a centralportion of an active region 8 of the MOSFET 51 in which the temperatureis at the highest. A source electrode 34 (source S) of the MOSFET 51 isarranged so as to cover a portion of the active region 8 other than thetemperature detecting diode 1, an anode metal wiring line 6, and acathode metal wiring line 7. An anode electrode pad 3 that is connectedto an anode A of the temperature detecting diode 1, a cathode electrodepad 4 that is connected to a cathode K of the temperature detectingdiode 1, and a gate electrode pad 5 that is connected to the gate G ofthe MOSFET 51 are formed in an outer circumferential portion of theactive region 8. The anode electrode pad 3, the cathode electrode pad 4,and the gate electrode pad 5 are arranged along, for example, the outercircumference of the active region 8. A drain electrode 35 (drain D) ofthe MOSFET 51 is arranged closer to the outer circumference of thesemiconductor device than the gate electrode pad 5.

The temperature detecting diode 1 is arranged so as to be separated fromthe anode electrode pad 3 and the cathode electrode pad 4. The anode A(FIG. 1(B)) of the temperature detecting diode 1 and the anode electrodepad 3 are connected to each other by the anode metal wiring line 6. Thecathode K of the temperature detecting diode 1 and the cathode electrodepad 4 are connected to each other by the cathode metal wiring line 7.The anode metal wiring line 6 and the cathode metal wiring line 7 extendfrom the temperature detecting diode 1 to the anode electrode pad 3 andthe cathode electrode pad 4 along, for example, the outer circumferenceof the active region 8, respectively. The protective diode 21 is formedon the side of the gate electrode pad 5 close to the inside of thesemiconductor device (the central portion side of the active region 8)along the gate electrode pad 5, the anode electrode pad 3, and thecathode electrode pad 4 and is connected to the gate electrode pad 5 andthe source electrode 34.

The protective diode 22 is formed on the side of the gate electrode pad5 close to the outer circumference of the semiconductor device and isconnected to the gate electrode pad 5 and the drain electrode 35. Asemiconductor layer and a capacitive component region (not illustrated)which is provided so as to come into contact with the lower surface ofthe semiconductor layer (a semiconductor-substrate-side surface (notillustrated)) and improves the static electricity resistance of thetemperature detecting diode 1 are formed in a portion below the anodemetal wiring line 6 (a portion that is arranged closer to thesemiconductor substrate than the anode metal wiring line 6 in the depthdirection of the plane of paper) and in a portion below the cathodemetal wiring line 7 (a portion closer to the semiconductor substratethan the cathode metal wiring line 7).

A capacitive component region (not illustrated) is also formed in aportion (a portion closer to the semiconductor substrate than thetemperature detecting diode 1) below temperature detecting diode 1 andin a portion (a portion closer to the semiconductor substrate than theprotective diodes 21 and 22) below the protective diodes 21 and 22.Therefore, it is possible to improve the static electricity resistanceof the temperature detecting diode 1 and the protective diodes 21 and22, without reducing the area of the active region 8. The temperaturedetecting diode 1 and the protective diodes 21 and 22 may beindependently formed according to the purpose of use or they may becombined with each other.

As described above, according to Embodiment 1, the capacitive componentregion is formed below the anode metal wiring line 6 that connects thetemperature detecting diode 1 and the anode electrode pad 3 and belowthe cathode metal wiring line 7 that connects the temperature detectingdiode 1 and the cathode electrode pad 4. Therefore, it is possible toimprove the static electricity resistance of the temperature detectingdiode 1. In addition, according to Embodiment 1, the capacitivecomponent region is formed below the temperature detecting diode 1 andthe protective diodes 21 and 22. Therefore, it is possible to improvethe static electricity resistance of the temperature detecting diode 1and the protective diodes 21 and 22, without reducing the area of theactive region 8.

Embodiment 2

The temperature detecting diode 1, the anode metal wiring line 6, andthe cathode metal wiring line 7 according to Embodiment 1 will bedescribed in detail as a semiconductor device according to Embodiment 2of the invention. FIGS. 2 and 4 are cross-sectional views illustratingthe structure of the semiconductor device according to Embodiment 2 ofthe invention. FIG. 3 is a circuit diagram illustrating the circuitstructure of the semiconductor device according to Embodiment 2 of theinvention. The planar structure of the semiconductor device according toEmbodiment 2 is the same as the planar structure in Embodiment 1illustrated in FIG. 1. FIG. 2 is a cross-sectional view illustrating across-sectional structure taken along the cutting line A-A′ of FIG.1(A). FIG. 3 is an equivalent circuit diagram of FIG. 2. FIG. 4 is across-sectional view illustrating a cross-sectional structure takenalong the cutting line B-B′ of FIG. 1(A).

As illustrated in FIGS. 2 to 4, in the semiconductor device according toEmbodiment 2, an n⁻ first semiconductor layer 9, which will be a driftregion of the MOSFET 51, is formed on the first main surface side of asemiconductor substrate 100. A p-type first semiconductor region 10,which will be a base region of the MOSFET 51, is formed in a surfacelayer (a surface layer close to the first main surface of the substrate;hereinafter, simply referred to as a surface layer) of the firstsemiconductor layer 9. An n⁺ drain region 38 is formed on the secondmain surface side of the semiconductor substrate 100. A drain electrode37 is formed on the surface of the drain region 38 (the second mainsurface of the semiconductor substrate 100).

A trench 31 is formed in the active region 8 in which a current flowswhen the semiconductor device is turned on so as to extend from thefirst main surface of the semiconductor substrate 100 to the firstsemiconductor layer 9 through the first semiconductor region 10. A gateinsulating film 32 is formed in the trench 31 along the inner wall ofthe trench 31. A gate electrode 33 is provided in the trench 31, withthe gate insulating film 32 interposed therebetween. The gate insulatingfilm 32 is an oxide film. The gate electrode 33 is covered with aninterlayer insulating film 17 which is made of polysilicon doped withimpurities (for example, n-type impurities). An n⁺ second semiconductorregion 11, which will be a source region, is formed adjacent to the sidewall of the trench 31. A source electrode 34 comes into contact(electrical contact) with the second semiconductor region 11 and thefirst semiconductor region 10.

A first insulating film 12 is formed on the first semiconductor region10 (that is, on the first main surface of the semiconductor substrate100) in a portion (a portion which is closer to the semiconductorsubstrate 100 than the temperature detecting diode 1) below thetemperature detecting diode 1. The first insulating film 12 is an oxidefilm. The thickness of the first insulating film 12 is equal to orgreater than the thickness of the gate insulating film 32 in terms ofvoltage breakdown due to, for example, static electricity orovervoltage. An n⁺ conductive layer 14 which is made of polysilicondoped with impurities is formed on the upper surface (the surfaceopposite to the semiconductor substrate 100) of the first insulatingfilm 12. A second insulating film 13 is formed on the upper surface ofthe conductive layer 14. The temperature detecting diode 1 which is madeof polysilicon is formed on the upper surface of the second insulatingfilm 13. The second insulating film 13 is an oxide film. The thicknessof the second insulating film 13 is equal to or greater than thethickness of the gate insulating film 32 in terms of voltage breakdowndue to, for example, electrostatic or overvoltage.

The temperature detecting diode 1 is formed by connecting a plurality ofzener diodes, each including a p⁺ layer 111 and an n⁺ layer 112, inseries to each other. The p⁺ layer 111 is made of, for example,polysilicon doped with boron (B). The n⁺ layer 112 is made of, forexample, polysilicon doped with arsenic (As) or phosphorus (P).

The anode metal wiring line 6 connects the temperature detecting diode 1and the anode electrode pad 3. In a portion (a portion which is closerto the semiconductor substrate 100 than the anode metal wiring line 6)below the anode metal wiring line 6, the first insulating film 12, whichis an oxide film having a thickness that is equal to or greater than thethickness of the gate insulating film 32, is formed on the firstsemiconductor region 10. The conductive layer 14 which is made ofpolysilicon is formed on the upper surface of the first insulating film12. The second insulating film 13, which is an oxide film having athickness that is equal to or greater than the thickness of the gateinsulating film 32, is formed on the upper surface of the conductivelayer 14. A first semiconductor layer 15 is formed on the upper surfaceof the second insulating film 13.

The cathode metal wiring line 7 connects the temperature detecting diode1 and the cathode electrode pad 4. In a portion (a portion which iscloser to the semiconductor substrate 100 than the cathode metal wiringline 7) below the cathode metal wiring line 7, the first having athickness that is equal to or greater than the thickness of the gateinsulating film 32, is formed on the first semiconductor region 10. Theconductive layer 14 which is made of polysilicon is formed on the uppersurface of the first insulating film 12. The second insulating film 13,which is an oxide film having a thickness that is equal to or greaterthan the thickness of the gate insulating film 32, is formed on theupper surface of the conductive layer 14. A second semiconductor layer16 is formed on the upper surface of the second insulating film 13.

The first semiconductor layer 15 and the second semiconductor layer 16are made of polysilicon doped with impurities. The thickness of thefirst semiconductor layer 15 and the second semiconductor layer 16 is inthe range of, for example, about 0.5 μm to 1 μm. The formation ofpolysilicon, ion implantation, and thermal diffusion for forming thefirst semiconductor layer 15 and the second semiconductor layer 16 areperformed in the same step as the formation of the temperature detectingdiode 1. The conductivity type of the first semiconductor layer 15 andthe second semiconductor layer 16 may be a p type or an n type. Whenpolysilicon is, for example, a p type, boron can be used as theimpurities added to polysilicon. When polysilicon is an n type, arsenicor phosphorus can be used as the impurities.

The first semiconductor layer 15 below the anode metal wiring line 6 andthe second semiconductor layer 16 below the cathode metal wiring line 7are formed on the same first semiconductor region 10, the same firstinsulating film 12, the same conductive layer 14, and the same secondinsulating film 13.

The temperature detecting diode 1, the first semiconductor layer 15below the anode metal wiring line 6, and the second semiconductor layer16 below the cathode metal wiring line 7 are formed on the same firstsemiconductor region 10, the same first insulating film 12, the sameconductive layer 14, and the same second insulating film 13.

The conductive layer 14 is made of, for example, polysilicon doped withn-type impurities at an impurity concentration of 4×10²⁰ cm⁻³ to 5×10²⁰cm⁻³. For example, the conductive layer 14 is formed at the same time asthe gate electrode 33 provided in the trench 31. Therefore, theconductive layer 14 may have a thickness required to fill the trench 31.In Embodiment 2 of the invention, the thickness of the conductive layer14 may be, for example, about 0.5 μm.

The conductive layer 14 is electrically insulated from the gateelectrode 33, the source electrode 34, the drain electrode 35, the anodeelectrode, and the cathode electrode by the interlayer insulating film17 and the second insulating film 13. In this way, it is possible toprevent the adverse effect of a surge voltage applied to each electrodeon the conductive layer 14.

As such, the first insulating film 12, the conductive layer 14, and thesecond insulating film 13 are formed on the first semiconductor region10 and the temperature detecting diode 1 is provided on the uppersurface of the second insulating film 13. Therefore, it is possible toform a capacitor C2 (C2 a to C2 j) which has the second insulating film13 between the temperature detecting diode 1 and the conductive layer 14as the capacitive component region. In addition, it is possible to forma capacitor C1 (C1 a to C1 e) which has the first insulating film 12between the conductive layer 14 and the first semiconductor region 10 asthe capacitive component region.

The first insulating film 12, the conductive layer 14, and the secondinsulating film 13 are formed on the first semiconductor region 10 andthe first semiconductor layer 15 is provided on the upper surface of thesecond insulating film 13. Therefore, it is possible to form a capacitorC4 which has, as the capacitive component region, the second insulatingfilm 13 provided between the conductive layer 14 and the firstsemiconductor layer 15 below the anode metal wiring line 6. In addition,the first insulating film 12, the conductive layer 14, and the secondinsulating film 13 are formed on the first semiconductor region 10 andthe second semiconductor layer 16 is provided on the upper surface ofthe second insulating film 13. Therefore, it is possible to form acapacitor C5 which has, as the capacitive component region, the secondinsulating film 13 provided between the conductive layer 14 and thesecond semiconductor layer 16 below the cathode metal wiring line 7. Inaddition, it is possible to form a capacitor C3 which has the firstinsulating film 12 between the conductive layer 14 and the firstsemiconductor region 10 as the capacitive component region.

In order to form the capacitor C4 and the capacitor C5 which have thesecond insulating film 13 as the capacitive component region, the anodemetal wiring line 6 and the cathode metal wiring line 7 can be directlyformed on the upper surface of the second insulating film 13, withoutforming the first semiconductor layer 15 and the second semiconductorlayer 16. However, this structure is not preferable for the followingreason. Before the anode metal wiring line 6 and the cathode metalwiring line 7 are formed, a step of covering the first main surface ofthe semiconductor substrate 100 with the interlayer insulating film 17and etching the interlayer insulating film 17 is performed. When thefirst semiconductor layer 15 and the second semiconductor layer 16 arenot formed on the upper surface of the second insulating film 13,etching residue or damage occurs in the surface of the second insulatingfilm 13 due to the step of etching the interlayer insulating film 17. Asa result, a variation in the thickness of the second insulating film 13occurs and a variation in the capacitive component region occurs.

Therefore, when the first semiconductor layer 15 and the secondsemiconductor layer 16 are formed on the upper surface of the secondinsulating film 13, it is possible to form the capacitor C4 and thecapacitor C5 having a stable capacitive component region, without beingaffected by the etching of the interlayer insulating film 17.

The thickness of the second insulating film 13 can be changed to adjustthe capacitance of the capacitor C2, the capacitor C4, and the capacitorC5, each having the second insulating film 13 as the capacitivecomponent region, to necessary static electricity resistance.

For example, when the temperature detecting diode 1 has an electrostaticbreakdown voltage of about 200 V, a capacitance of about 90 pF isrequired. Therefore, the thickness of the second insulating film 13 maybe equal to or greater than the thickness of the gate insulating film 32and equal to or less than 1000 Å.

The thickness of the first insulating film 12 may be equal to or greaterthan the thickness of the gate insulating film 32. The thickness of thefirst insulating film 12 may be equal to or greater than the thicknessof the gate insulating film 32 and equal to or less than 1000 Å, inorder to use the first insulating film 12 between the conductive layer14 and the first semiconductor region 10 as the capacitive componentregion. When the first insulating film 12 is not used as the capacitivecomponent region, the upper limit of the thickness of the firstinsulating film 12 is not particularly limited. For example, thethickness of the first insulating film 12 can be equal to the thicknessof a field oxide film (not illustrated) which is formed on the firstmain surface (surface) of the semiconductor substrate 100.

As described above, according to Embodiment 2, since the capacitivecomponent region is formed between the conductive layer 14 and thetemperature detecting diode 1, it is possible to improve the staticelectricity resistance of the temperature detecting diode 1, withoutincreasing the area of the temperature detecting diode 1. In addition,according to Embodiment 2, since the capacitive component region isformed between the conductive layer 14 and the first semiconductorregion 10 below the temperature detecting diode 1, it is possible tofurther improve the static electricity resistance of the temperaturedetecting diode 1.

According to Embodiment 2, since the capacitive component region isformed between the conductive layer 14 and the first and secondsemiconductor layers 15 and 16 below the anode metal wiring line 6 andthe cathode metal wiring line 7, it is possible to improve the staticelectricity resistance of the temperature detecting diode 1, withoutreducing the area of the active region 8. In addition, according toEmbodiment 2, since the capacitive component region is formed betweenthe conductive layer 14 and the first semiconductor region 10 below theanode metal wiring line 6 and the cathode metal wiring line 7, it ispossible to further improve the static electricity resistance of thetemperature detecting diode 1.

Embodiment 3

The protective diode 21 according to Embodiment 1 will be described indetail as a semiconductor device according to Embodiment 3 of theinvention. FIG. 5 is a diagram illustrating the structure of thesemiconductor device according to Embodiment 3 of the invention. Theplanar structure of the semiconductor device according to Embodiment 3is the same as the planar structure in Embodiment 1 illustrated inFIG. 1. FIG. 5(A) is a cross-sectional view illustrating across-sectional structure taken along the cutting line C-C′ of FIG. 1(A)and FIG. 5(B) is an equivalent circuit diagram of FIG. 5(A).

As illustrated in FIG. 5, in the semiconductor device according toEmbodiment 3, the n⁻ first semiconductor layer 9, which will be thedrift region of the MOSFET 51, is formed on the first main surface sideof the semiconductor substrate 100. The p-type first semiconductorregion 10, which will be the base region of the MOSFET 51, is formed ina surface layer of the first semiconductor layer 9. The n⁺ drain region38 is formed on the second main surface side of the semiconductorsubstrate 100. The drain electrode 37 is formed on the surface of thedrain region 38.

The trench 31 is formed in the active region 8 so as to extend from thefirst main surface of the semiconductor substrate 100 to the firstsemiconductor layer 9 through the first semiconductor region 10. Thegate insulating film 32 is formed in the trench 31 along the inner wallof the trench 31. In addition, the gate electrode 33 is provided in thetrench 31, with the gate insulating film 32 interposed therebetween. Thegate insulating film 32 is an oxide film. The gate electrode 33 iscovered with the interlayer insulating film 17 which is made ofpolysilicon doped with impurities. The n⁺ second semiconductor region11, which will be a source region, is formed adjacent to the side wallof the trench 31. The source electrode 34 comes into contact with thesecond semiconductor region 11 and the first semiconductor region 10.

The protective diode 21 is arranged between the source electrode 34 andthe gate electrode pad 5. The first insulating film 12 is formed on thefirst semiconductor region 10 below the protective diode 21. The firstinsulating film 12 is an oxide film. The thickness of the firstinsulating film 12 is equal to or greater than the thickness of the gateinsulating film 32 in terms of voltage breakdown due to, for example,static electricity or overvoltage. The n⁺ conductive layer 14 which ismade of polysilicon doped with impurities is formed on the upper surfaceof the first insulating film 12. The second insulating film 13 is formedon the upper surface of the conductive layer 14. The protective diode 21which is made of polysilicon is formed on the upper surface of thesecond insulating film 13. The protective diode 21 is connected betweenthe gate G (gate electrode pad 5) and the source S (source electrode34). The second insulating film 13 is an oxide film. The thickness ofthe second insulating film 13 is equal to or greater than the thicknessof the gate insulating film 32 in terms of voltage breakdown due to, forexample, static electricity or overvoltage.

The protective diode 21 provided between the gate G and the source S isa multi-stage bidirectional zener diode including the p⁺ layer 111 andthe n⁺ layer 112. That is, in the protective diode 21, the p⁺ layer 111and the n⁺ layer 112 are alternately arranged in the direction in whichthe p⁺ layer 111 and the n⁺ layer 112 are arranged in a line. The n⁺layers 112 are provided at both ends of the protective diode 21. The n⁺layer 112 provided at one end is connected to the gate G and the n⁺layer 112 provided at the other end is connected to the source S. The p⁺layer 111 is made of polysilicon doped with, for example, boron. The n⁺layer 112 is made of polysilicon doped with, for example, arsenic orphosphorus.

The conductive layer 14 is made of, for example, polysilicon doped withn-type impurities at an impurity concentration of 4×10²⁰ cm⁻³ to 5×10²⁰cm⁻³. For example, the conductive layer 14 is formed at the same time asthe gate electrode 33 provided in the trench 31. Therefore, theconductive layer 14 may have a thickness required to fill the trench 31.In this embodiment, the thickness of the conductive layer 14 may be, forexample, about 0.5 μm.

The conductive layer 14 is electrically insulated from the gateelectrode 33, the source electrode 34, the drain electrode 35, the anodeelectrode, and the cathode electrode by the interlayer insulating film17 and the second insulating film 13. Therefore, it is possible toprevent the adverse effect of a surge voltage applied to each electrodeon the conductive layer 14.

As such, the first insulating film 12, the conductive layer 14, and thesecond insulating film 13 are formed on the first semiconductor region10 and the protective diode 21 is provided on the upper surface of thesecond insulating film 13. Therefore, it is possible to form a capacitorC7 (C7 a to C7 e) which has the second insulating film 13 providedbetween the protective diode 21 and the conductive layer 14 as acapacitive component region. In addition, it is possible to form acapacitor C6 which has the first insulating film 12 provided between theconductive layer 14 and the first semiconductor region 10 as acapacitive component region.

The thickness of the second insulating film 13 can be changed to adjustthe capacitance of the capacitor C7, which has the second insulatingfilm 13 as the capacitive component region, to necessary staticelectricity resistance. For example, when the protective diode 21 has anelectrostatic breakdown voltage of about 200 V, a capacitance of about90 pF is required. Therefore, the thickness of the second insulatingfilm 13 may be equal to or greater than the thickness of the gateinsulating film 32 and equal to or less than 1000 Å.

The thickness of the first insulating film 12 may be equal to or greaterthan the thickness of the gate insulating film 32. The thickness of thefirst insulating film 12 may be equal to or greater than the thicknessof the gate insulating film 32 and equal to or less than 1000 Å, inorder to use the first insulating film 12 between the conductive layer14 and the first semiconductor region 10 as the capacitive componentregion. When the first insulating film 12 is not used as the capacitivecomponent region, the upper limit of the thickness of the firstinsulating film 12 is not particularly limited. For example, thethickness of the first insulating film 12 can be equal to the thicknessof a field oxide film (not illustrated) which is formed on the firstmain surface of the semiconductor substrate 100.

As described above, according to Embodiment 3, since the capacitivecomponent region is formed between the conductive layer 14 and theprotective diode 21, it is possible to improve the static electricityresistance of the protective diode 21, without increasing the area ofthe protective diode 21. In addition, according to Embodiment 3, sincethe capacitive component region is formed between the conductive layer14 and the first semiconductor region 10 below the protective diode 21,it is possible to further improve the static electricity resistance ofthe protective diode 21.

Embodiment 4

The protective diode 22 according to Embodiment 1 will be described indetail as a semiconductor device according to Embodiment 4 of theinvention. FIG. 6 is a diagram illustrating the structure of thesemiconductor device according to Embodiment 4 of the invention. Theplanar structure of the semiconductor device according to Embodiment 4is the same as the planar structure in Embodiment 1 illustrated inFIG. 1. FIG. 6(A) is a cross-sectional view illustrating across-sectional structure taken along the cutting line D-D′ of FIG. 1(A)and FIG. 6(B) is an equivalent circuit diagram of FIG. 6(A).

As illustrated in FIG. 6, in the semiconductor device according toEmbodiment 4, the n⁻ first semiconductor layer 9, which will be thedrift region of the MOSFET 51, is formed on the first main surface sideof the semiconductor substrate 100. The p-type first semiconductorregion 10, which will be the base region of the MOSFET 51, is formed ina surface layer of the first semiconductor layer 9 close to the gateelectrode pad 5 (the inside). An n⁺ drain region 36 is formed in asurface layer of the first semiconductor layer 9 close to a drainelectrode 35 (outer circumferential side). The n⁺ drain region 38 isformed on the second main surface side of the semiconductor substrate100. The drain electrode 37 is formed on the surface of the drain region38.

The protective diode 22 is arranged between the gate electrode pad 5 andthe drain electrode 35. The first insulating film 12 is formed on thefirst main surface of the semiconductor substrate 100 so as to extendover the first semiconductor region 10 close to the gate electrode pad 5and the drain region 36 close to the drain electrode 35. The firstinsulating film 12 is an oxide film. The thickness of the firstinsulating film 12 is equal to or greater than the thickness of the gateinsulating film 32 in terms of voltage breakdown due to, for example,static electricity or overvoltage. The n⁺ conductive layer 14 which ismade of polysilicon doped with impurities is formed on the upper surfaceof the first insulating film 12. The second insulating film 13 is formedon the upper surface of the conductive layer 14. The protective diode 22which is made of polysilicon is formed on the upper surface of thesecond insulating film 13. The protective diode 22 is connected betweenthe gate G (gate electrode pad 5) and the drain D (drain electrode 35).The second insulating film 13 is an oxide film. The thickness of thesecond insulating film 13 is equal to or greater than the thickness ofthe gate insulating film 32 in terms of voltage breakdown due to, forexample, electrostatic or overvoltage.

The protective diode 22 provided between the gate G and the drain D is amulti-stage bidirectional zener diode including the p⁺ layer 111 and then⁺ layer 112. That is, in the protective diode 22, the p⁺ layer 111 andthe n⁺ layer 112 are alternately arranged in the direction in which thep⁺ layer 111 and the n⁺ layer 112 are arranged in a line. The n⁺ layers112 are provided at both ends of the protective diode 22. The n⁺ layer112 provided at one end is connected to the gate G and the n⁺ layer 112provided at the other end is connected to the drain D. The p⁺ layer 111is made of polysilicon doped with, for example, boron. The n⁺ layer 112is made of polysilicon doped with, for example, arsenic or phosphorus.

The conductive layer 14 is made of, for example, polysilicon doped withn-type impurities at an impurity concentration of 4×10²⁰ cm⁻³ to 5×10²⁰cm⁻³. For example, the conductive layer 14 is formed at the same time asthe gate electrode 33 provided in the trench 31. Therefore, theconductive layer 14 may have a thickness required to fill the trench 31.In this embodiment, the thickness of the conductive layer 14 may be, forexample, about 0.5 μm.

The conductive layer 14 is electrically insulated from the gateelectrode 33, the source electrode 34, the drain electrode 35, the anodeelectrode, and the cathode electrode by the interlayer insulating film17 and the second insulating film 13. Therefore, it is possible toprevent the adverse effect of a surge voltage applied to each electrodeon the conductive layer 14.

As such, the first insulating film 12, the conductive layer 14, and thesecond insulating film 13 are formed on the first semiconductor region10 and the protective diode 22 is provided on the upper surface of thesecond insulating film 13. Therefore, it is possible to form a capacitorC9 (C9 a to C9 e) which has the second insulating film 13 providedbetween the protective diode 22 and the conductive layer 14 as acapacitive component region. In addition, it is possible to form acapacitor C8 which has the first insulating film 12 provided between theconductive layer 14 and the semiconductor substrate 100 as a capacitivecomponent region.

The thickness of the second insulating film 13 can be changed to adjustthe capacitance of the capacitor C9, which has the second insulatingfilm 13 as the capacitive component region, to necessary staticelectricity resistance. For example, when the protective diode 22 has anelectrostatic breakdown voltage of about 200 V, a capacitance of about90 pF is required. Therefore, the thickness of the second insulatingfilm 13 may be equal to or greater than the thickness of the gateinsulating film 32 and equal to or less than 1000 Å.

The thickness of the first insulating film 12 may be equal to or greaterthan the thickness of the gate insulating film 32. The thickness of thefirst insulating film 12 may be equal to or greater than the thicknessof the gate insulating film 32 and equal to or less than 1000 Å, inorder to use the first insulating film 12 between the conductive layer14 and the semiconductor substrate 100 as the capacitive componentregion. When the first insulating film 12 is not used as the capacitivecomponent region, the upper limit of the thickness of the firstinsulating film 12 is not particularly limited. For example, thethickness of the first insulating film 12 can be equal to the thicknessof a field oxide film (not illustrated) which is formed on the firstmain surface of the semiconductor substrate 100.

As described above, according to Embodiment 4, the same effect as thatin Embodiments 1 to 3 is obtained. In addition, according to Embodiment4, since the capacitive component region is formed between theconductive layer 14 and the protective diode 22, it is possible toimprove the static electricity resistance of the protective diode 22,without increasing the area of the protective diode 22. Furthermore,according to Embodiment 4, since the capacitive component region isformed between the first semiconductor region 10 and the conductivelayer 14 below the protective diode 22, it is possible to furtherimprove the static electricity resistance of the protective diode 22.

Embodiment 5

A semiconductor device according to Embodiment 5 will be described. FIG.7 is a cross-sectional view illustrating the structure of thesemiconductor device according to Embodiment 5 of the invention. FIG. 8is a cross-sectional view illustrating another example of the structureof the semiconductor device according to Embodiment 5 of the invention.The semiconductor device according to Embodiment 5 is a modification ofthe semiconductor device according to Embodiment 2. The planar structureof the semiconductor device according to Embodiment 5 is the same as theplanar structure in Embodiment 1 illustrated in FIG. 1. Thesemiconductor device according to Embodiment 5 differs from thesemiconductor device according to Embodiment 2 in that a portion of aninterlayer insulating film 17 interposed between a first semiconductorlayer 15 and a second semiconductor layer 16 is a capacitive componentregion.

FIG. 7 is a cross-sectional view illustrating the cross-sectionalstructure of the semiconductor device according to Embodiment 5 takenalong the cutting line B-B′ of FIG. 1. The gap between the firstsemiconductor layer 15 below an anode metal wiring line 6 and the secondsemiconductor layer 16 below a cathode metal wiring line 7 is narrowedto form a capacitor C10 which has the interlayer insulating film 17provided between the first semiconductor layer 15 and the secondsemiconductor layer 16 as the capacitive component region. The gapbetween the first semiconductor layer 15 and the second semiconductorlayer 16 may be, for example, about 0.5 μm.

FIG. 8 is a cross-sectional view illustrating another example of thecross-sectional structure of the semiconductor device according toEmbodiment 5 taken along the cutting line B-B′ of FIG. 1. The interlayerinsulating film 17 is formed such that a concave portion is providedbetween the first semiconductor layer 15 and the second semiconductorlayer 16. Then, the anode metal wiring line 6 is formed so as to fillthe concave portion of the interlayer insulating film 17. In this way,it is possible to form a capacitor C11 which has the interlayerinsulating film 17 between the anode metal wiring line 6 and the secondsemiconductor layer 16 as a capacitive component region.

In the semiconductor devices illustrated in FIGS. 7 and 8, it ispossible to form the capacitive component region below the anode metalwiring line 6 and the cathode metal wiring line 7 which are providedfrom the temperature detecting diode 1 to the anode electrode pad 3 andthe cathode electrode pad 4, without reducing the area of the activeregion 8, and to improve the static electricity resistance of thetemperature detecting diode 1.

As described above, according to Embodiment 5, the same effect as thatin Embodiments 1 to 4 is obtained.

Embodiment 6

A semiconductor device according to Embodiment 6 will be described.FIGS. 9 and 10 are cross-sectional views illustrating the structure ofthe semiconductor device according to Embodiment 6 of the invention. Thesemiconductor device according to Embodiment 6 is a modification of thesemiconductor device according to Embodiment 2. The planar structure ofthe semiconductor device according to Embodiment 6 is the same as theplanar structure in Embodiment 1 illustrated in FIG. 1. Thesemiconductor device according to Embodiment 6 differs from thesemiconductor device according to Embodiment 2 in that a conductivelayer 14 is divided into a plurality of parts by a second insulatingfilm 13 which passes through the conductive layer 14 in the thicknessdirection.

FIG. 9 is a cross-sectional view illustrating the cross-sectionalstructure of a temperature detecting diode 1 taken along the cuttingline A-A′ of FIG. 1 in the semiconductor device according to Embodiment6. The conductive layer 14 is divided into a conductive layer 14 a and aconductive layer 14 b for each conductivity-type layer (a p⁺ layer 111and an n⁺ layer 112) of the temperature detecting diode 1 which isformed on the conductive layer 14 with the second insulating film 13interposed therebetween. Specifically, the conductive layer 14 isdivided into the conductive layer 14 a which faces the p⁺ layer 111,with the second insulating film 13 interposed therebetween, and theconductive layer 14 b which faces the n⁺ layer 112, with the secondinsulating film 13 interposed therebetween. A space between the dividedconductive layers 14 a and 14 b is filled with the second insulatingfilm 13. Therefore, it is possible to form a capacitor C12 which has thesecond insulating film 13 between the conductive layer 14 a and theconductive layer 14 b as a capacitive component region.

FIG. 10 is a cross-sectional view illustrating the cross-sectionalstructure of the semiconductor device according to Embodiment 6 takenalong the cutting line B-B′ of FIG. 1. The conductive layer 14 isdivided into a conductive layer 14 a close to the first semiconductorlayer 15 that is formed on the conductive layer 14, with the secondinsulating film 13 interposed therebetween, and a conductive layer 14 bclose to the second semiconductor layer 16 that is formed on theconductive layer 14, with the second insulating film 13 interposedtherebetween. That is, the conductive layer 14 is divided into theconductive layer 14 a which faces the first semiconductor layer 15, withthe second insulating film 13 interposed therebetween, and theconductive layer 14 b which faces the second semiconductor layer 16,with the second insulating film 13 interposed therebetween. A spacebetween the divided conductive layers 14 a and 14 b is filled with thesecond insulating film 13.

It is possible to form a capacitor C13 which has the second insulatingfilm 13 between the conductive layer 14 a and the conductive layer 14 bas a capacitive component region. Reference numerals C3 a and C3 bdenote capacitors which have the first insulating film 12 between theconductive layers 14 a and 14 b and the first semiconductor region 10 asa capacitive component region. As illustrated in FIGS. 9 and 10, theconductive layer 14 may be provided in portions which face eachconductivity-type layer forming the element that is arranged on theupper surface of the conductive layer 14, with the second insulatingfilm 13 interposed therebetween. For example, this structure can also beapplied to the protective diode 21 between the gate G and the source Sdescribed in Embodiment 3 or the protective diode 22 between the gate Gand the drain D described in Embodiment 4.

As described above, according to Embodiment 6, the same effect as thatin Embodiments 1 to 5 is obtained.

Embodiment 7

A semiconductor device according to Embodiment 7 of the invention willbe described. FIG. 11 is a diagram illustrating the structure of thesemiconductor device according to Embodiment 7 of the invention. Thesemiconductor device according to Embodiment 7 is a modification ofEmbodiment 3. The planar structure of the semiconductor device accordingto Embodiment 7 is the same as the semiconductor device according toEmbodiment 1 illustrated in FIG. 1. The semiconductor device accordingto Embodiment 7 differs from the semiconductor device according toEmbodiment 3 in that a conductive layer 14 is divided into a conductivelayer 14 a, on which the protective diode 21 is arranged, and aconductive layer 14 b, on which the protective diode 21 is not arranged,by a second insulating film 13 which passes through the conductive layer14 in the thickness direction.

FIG. 11(A) is a cross-sectional view illustrating the cross-sectionalstructure of the semiconductor device according to Embodiment 7 takenalong the cutting line C-C′ of FIG. 1. FIG. 11(B) is an equivalentcircuit diagram of FIG. 11(A). The conductive layer 14 is divided intothe conductive layers 14 a and 14 b, as illustrated in FIG. 11. Thesecond insulating film 13, which is an oxide film with a thickness thatis equal to or greater than the thickness of a gate insulating film 32,is formed on the upper surface of the divided conductive layer 14 a. Theprotective diode 21 is formed on the upper surface of the secondinsulating film 13. The conductive layer 14 b is connected to a sourceelectrode 34.

In this case, the conductive layer 14 a is electrically insulated from agate electrode 33, the source electrode 34, a drain electrode 35, ananode electrode, and a cathode electrode by an interlayer insulatingfilm 17 and the second insulating film 13. It is possible to form acapacitor C14 which has the interlayer insulating film 17 between theconductive layer 14 a and the conductive layer 14 b as a capacitivecomponent region.

As described above, according to Embodiment 7, the same effect as thatin Embodiments 1 to 6 is obtained.

Embodiment 8

A semiconductor device according to Embodiment 8 of the invention willbe described. FIGS. 12 and 14 are cross-sectional views illustrating thestructure of the semiconductor device according to Embodiment 8 of theinvention. FIG. 13 is a circuit diagram illustrating the circuitstructure of the semiconductor device according to Embodiment 8 of theinvention. The planar structure of the semiconductor device according toEmbodiment 8 is the same as the planar structure in Embodiment 1illustrated in FIG. 1. FIG. 12 is a cross-sectional view illustratingthe cross-sectional structure of the semiconductor device according toEmbodiment 8 taken along the cutting line A-A′ of FIG. 1. FIG. 13 is anequivalent circuit diagram of FIG. 12. FIG. 14 is a cross-sectional viewillustrating the cross-sectional structure of the semiconductor deviceaccording to Embodiment 8 taken along the cutting line B-B′ of FIG. 1.The semiconductor device according to Embodiment 8 of the inventiondiffers from the semiconductor device according to Embodiment 2 of theinvention in that a conductive layer 14 and a second insulating film 13are not provided and a temperature detecting diode 1, an anode metalwiring line 6, and a cathode metal wiring line 7 are formed on the uppersurface of a first insulating film 12.

As illustrated in FIGS. 12 to 14, in the semiconductor device accordingto Embodiment 8, an n⁻ first semiconductor layer 9, which will be adrift region of a MOSFET 51, is formed on the first main surface side ofa semiconductor substrate 100. A p-type first semiconductor region 10,which will be a base region of the MOSFET 51, is formed in a surfacelayer of the first semiconductor layer 9. An n⁺ drain region 38 isformed on the second main surface side of the semiconductor substrate100. A drain electrode 37 is formed on the surface of the drain region38.

A trench 31 is formed in an active region 8 so as to extend from thefirst main surface of the semiconductor substrate 100 to the firstsemiconductor layer 9 through the first semiconductor region 10. A gateinsulating film 32 is formed in the trench 31 along the inner wall ofthe trench 31. A gate electrode 33 is provided in the trench 31, withthe gate insulating film 32 interposed therebetween. The gate insulatingfilm 32 is an oxide film. The gate electrode 33 is covered with aninterlayer insulating film 17 which is made of polysilicon doped withimpurities. An n⁺ second semiconductor region 11, which will be a sourceregion, is formed adjacent to the side wall of the trench 31. A sourceelectrode 34 comes into contact with the second semiconductor region 11and the first semiconductor region 10.

The first insulating film 12 is formed on the first semiconductor region10 below the temperature detecting diode 1. The temperature detectingdiode 1 which is made of polysilicon is formed on the upper surface ofthe first insulating film 12. The first insulating film 12 is an oxidefilm. The thickness of the first insulating film 12 is equal to orgreater than the thickness of the gate insulating film 32 in terms ofvoltage breakdown due to, for example, static electricity orovervoltage.

The temperature detecting diode 1 is formed by connecting a plurality ofzener diodes, each having a p⁺ layer 111 and an n⁺ layer 112, in seriesto each other. The p⁺ layer 111 is made of polysilicon doped with, forexample, boron. The n⁺ layer 112 is made of polysilicon doped with, forexample, arsenic or phosphorus.

Below the anode metal wiring line 6 which connects the temperaturedetecting diode 1 and an anode electrode pad 3, the first insulatingfilm 12, which is an oxide film with a thickness that is equal to orgreater than the thickness of the gate insulating film 32, is formed onthe first semiconductor region 10. A first semiconductor layer 15 isformed on the upper surface of the first insulating film 12.

Below the cathode metal wiring line 7 which connects the temperaturedetecting diode 1 and a cathode electrode pad 4, the first insulatingfilm 12, which is an oxide film with a thickness that is equal to orgreater than the thickness of the gate insulating film 32, is formed onthe first semiconductor region 10. A second semiconductor layer 16 isformed on the upper surface of the first insulating film 12.

The first semiconductor layer 15 and the second semiconductor layer 16are made of polysilicon doped with impurities. The thickness of thefirst semiconductor layer 15 and the second semiconductor layer 16 is inthe range of, for example, about 0.5 μm to 1 μm. The formation ofpolysilicon, ion implantation, and thermal diffusion for forming thefirst semiconductor layer 15 and the second semiconductor layer 16 areperformed in the same step as the formation of the temperature detectingdiode 1. The conductivity type of the first semiconductor layer 15 andthe second semiconductor layer 16 may be a p type or an n type. Whenpolysilicon is, for example, a p type, boron can be used as theimpurities added to polysilicon. When polysilicon is an n type, arsenicor phosphorus can be used as the impurities.

The first semiconductor layer 15 below the anode metal wiring line 6 andthe second semiconductor layer 16 below the cathode metal wiring line 7are formed on the same first semiconductor region 10 and the same firstinsulating film 12. In addition, the temperature detecting diode 1, thefirst semiconductor layer 15 below the anode metal wiring line 6, andthe second semiconductor layer 16 below the cathode metal wiring line 7are formed on the same first semiconductor region 10 and the same firstinsulating film 12.

As such, since the first insulating film 12 is formed on the firstsemiconductor region 10 and the temperature detecting diode 1 isprovided on the upper surface of the first insulating film 12, it ispossible to form a capacitor C41 (C41 a to C41 j), which has the firstinsulating film 12 between the first semiconductor region 10 and thetemperature detecting diode 1 as a capacitive component region, belowthe temperature detecting diode 1.

Since the first insulating film 12 is formed on the first semiconductorregion 10 and the first semiconductor layer 15 is provided on the upperlayer of the first insulating film 12, it is possible to form acapacitor C42, which has the first insulating film 12 between the firstsemiconductor region 10 and the first semiconductor layer 15 as acapacitive component region, below the anode metal wiring line 6.

Since the first insulating film 12 is formed on the first semiconductorregion 10 and the second semiconductor layer 16 is provided on the upperlayer of the first insulating film 12, it is possible to form acapacitor C43, which has the first insulating film 12 between the firstsemiconductor region 10 and the second semiconductor layer 16 as acapacitive component region, below the cathode metal wiring line 7.

In order to use the first insulating film 12 as the capacitive componentregion, the anode metal wiring line 6 and the cathode metal wiring line7 can be directly formed on the first insulating film 12, withoutforming the first semiconductor layer 15 and the second semiconductorlayer 16. However, this structure is not preferable for the followingreason. Before the anode metal wiring line 6 and the cathode metalwiring line 7 are formed, a step of covering the first main surface ofthe semiconductor substrate 100 with the interlayer insulating film 17and etching the interlayer insulating film 17 is performed. When thefirst semiconductor layer 15 and the second semiconductor layer 16 arenot formed on the upper surface of the first insulating film 12, etchingresidue or damage occurs in the surface of the first insulating film 12due to the step of etching the interlayer insulating film 17. As aresult, a variation in the thickness of the first insulating film 12occurs and a variation in the capacitive component region occurs.

Therefore, when the first semiconductor layer 15 and the secondsemiconductor layer 16 are formed on the upper surface of the firstinsulating film 12, it is possible to form the capacitor C42 and thecapacitor C43 having the stable capacitive component region, withoutbeing affected by the etching of the interlayer insulating film 17.

The thickness of the first insulating film 12 can be changed to adjustthe capacitance of the capacitor C41, the capacitor C42, and thecapacitor C43, each having the first insulating film 12 as thecapacitive component region, to necessary static electricity resistance.

For example, when the temperature detecting diode 1 has an electrostaticbreakdown voltage of about 200 V, a capacitance of about 90 pF isrequired. Therefore, the thickness of the first insulating film 12 maybe equal to or greater than the thickness of the gate insulating film 32and equal to or less than 1000 Å.

As described above, according to Embodiment 8, since the capacitivecomponent region is formed between the temperature detecting diode 1 andthe first semiconductor region 10 below the temperature detecting diode1, it is possible to improve the static electricity resistance of thetemperature detecting diode 1, without increasing the area of thetemperature detecting diode 1.

According to Embodiment 8, since the capacitive component region isformed between the first semiconductor region 10 below the anode metalwiring line 6 and the cathode metal wiring line 7 and the first andsecond semiconductor layers 15 and 16, it is possible to improve thestatic electricity resistance of the temperature detecting diode 1,without reducing the area of the active region 8.

Embodiment 9

A semiconductor device according to Embodiment 9 will be described. FIG.15 is a diagram illustrating the structure of the semiconductor deviceaccording to Embodiment 9 of the invention. The planar structure of thesemiconductor device according to Embodiment 9 is the same as the planarstructure in the Embodiment 1 illustrated in FIG. 1. FIG. 15(A) is across-sectional view illustrating the cross-sectional structure of thesemiconductor device according to Embodiment 9 taken along the cuttingline C-C′ of FIG. 1. FIG. 15(B) is an equivalent circuit diagram of FIG.15(A). The semiconductor device according to Embodiment 9 of theinvention differs from the semiconductor device according to Embodiment3 in that a conductive layer 14 and a second insulating film 13 are notprovided and a protective diode 21 is formed on the upper surface of afirst insulating film 12.

As illustrated in FIG. 15, in the semiconductor device according toEmbodiment 9, an n⁻ first semiconductor layer 9, which will be a driftregion of a MOSFET 51, is formed on the first main surface side of asemiconductor substrate 100. A p-type first semiconductor region 10,which will be a base region of the MOSFET 51, is formed in a surfacelayer of the first semiconductor layer 9. An n⁺ drain region 38 isformed on the second main surface side of the semiconductor substrate100. A drain electrode 37 is formed on the surface of the drain region38.

A trench 31 is formed in an active region 8 so as to extend from thefirst main surface of the semiconductor substrate 100 to the firstsemiconductor layer 9 through the first semiconductor region 10. A gateinsulating film 32 is formed in the trench 31 along the inner wall ofthe trench 31. A gate electrode 33 is provided in the trench 31, withthe gate insulating film 32 interposed therebetween. The gate insulatingfilm 32 is an oxide film. The gate electrode 33 is covered with aninterlayer insulating film 17 which is made of polysilicon doped withimpurities. An n⁺ second semiconductor region 11, which will be a sourceregion, is formed adjacent to the side wall of the trench 31. A sourceelectrode 34 comes into contact with the second semiconductor region 11and the first semiconductor region 10.

The protective diode 21 is arranged between the source electrode 34 andthe gate electrode pad 5. Below the protective diode 21, the firstinsulating film 12 is formed on the first semiconductor region 10. Thefirst insulating film 12 is an oxide film. The thickness of the firstinsulating film 12 is equal to or greater than the thickness of the gateinsulating film 32 in terms of voltage breakdown due to, for example,static electricity or overvoltage. The protective diode 21 which is madeof polysilicon is formed on the upper surface of the first insulatingfilm 12. The protective diode 21 is connected to between a gate G and asource S.

The protective diode 21 provided between the gate G and the source S isa multi-stage bidirectional zener diode including a p⁺ layer 111 and an⁺ layer 112. The p⁺ layer 111 is made of polysilicon doped with, forexample, boron. The n⁺ layer 112 is made of polysilicon doped with, forexample, arsenic or phosphorus.

As such, since the first insulating film 12 is formed on the firstsemiconductor region 10 and the protective diode 21 is provided on theupper surface of the first insulating film 12, it is possible to form acapacitor C44 (C44 a to C44 e), which has the first insulating film 12between the first semiconductor region 10 and the protective diode 21 asa capacitive component region, below the protective diode 21 providedbetween the gate G and the source S.

The thickness of the first insulating film 12 can be changed to adjustthe capacitance of the capacitor C44 having the first insulating film 12as the capacitive component region to necessary static electricityresistance. For example, when the protective diode 21 has anelectrostatic breakdown voltage of about 200 V, a capacitance of about90 pF is required. Therefore, that the thickness of the first insulatingfilm 12 may be equal to or greater than the thickness of the gateinsulating film 32 and equal to or less than 1000 Å.

As described above, according to Embodiment 9, since the capacitivecomponent region is formed between the first semiconductor region 10 andthe protective diode 21 below the protective diode 21 provided betweenthe gate G and the source S, it is possible to improve the staticelectricity resistance of the protective diode 21, without increasingthe area of the protective diode 21.

Embodiment 10

A semiconductor device according to Embodiment 10 of the invention willbe described. FIG. 16 is a diagram illustrating the structure of thesemiconductor device according to Embodiment 10 of the invention. Theplanar structure of the semiconductor device according to Embodiment 10is the same as the planar structure in Embodiment 1 illustrated inFIG. 1. FIG. 16(A) is a cross-sectional view illustrating thecross-sectional structure of the semiconductor device according toEmbodiment 10 taken along the cutting line D-D′ of FIG. 1. FIG. 16(B) isan equivalent circuit diagram of FIG. 16(A). The semiconductor deviceaccording to Embodiment 10 of the invention differs from thesemiconductor device according to Embodiment 4 in that a conductivelayer 14 and a second insulating film 13 are not provided and aprotective diode 22 is formed on the upper surface of a first insulatingfilm 12.

As illustrated in FIG. 16, in the semiconductor device according toEmbodiment 10, an n⁻ first semiconductor layer 9, which will be a driftregion of a MOSFET 51, is formed on the first main surface side of asemiconductor substrate 100. A p-type first semiconductor region 10,which will be a base region of the MOSFET 51, is formed in the firstsemiconductor layer 9 close to the gate electrode pad 5. An n⁺ drainregion 36 is formed in a surface layer of the first semiconductor layer9 which is close to a drain electrode 35. A drain region 38 is formed onthe second main surface side of the semiconductor substrate 100. A drainelectrode 37 is formed on the surface of the drain region 38.

The protective diode 22 is arranged between a gate electrode pad 5 andthe drain electrode 35. The first insulating film 12 is formed on thefirst main surface of the semiconductor substrate 100 so as to extendover the first semiconductor region 10 close to the gate electrode pad 5and the drain region 36 close to the drain electrode 35. A protectivediode 22 which is made of polysilicon is formed on the upper surface ofthe first insulating film 12. The protective diode 22 is connectedbetween a gate G and a drain D. The first insulating film 12 is an oxidefilm. The thickness of the first insulating film 12 is equal to orgreater than the thickness of the gate insulating film 32 in terms ofvoltage breakdown due to, for example, static electricity orovervoltage.

The protective diode 22 connected between the gate G and the drain D isa multi-stage bidirectional zener diode including a p⁺ layer 111 and ann⁺ layer 112. The p⁺ layer 111 is made of polysilicon doped with, forexample, boron. The n⁺ layer 112 is made of polysilicon doped with, forexample, arsenic or phosphorus.

As such, the first insulating film 12 is formed on the firstsemiconductor region 10 and the protective diode 22 is provided on theupper surface of the first insulating film 12. Therefore, it is possibleto form a capacitor C45 (C45 a to C45 e), which has the first insulatingfilm 12 between the semiconductor substrate 100 and the protective diode22 as a capacitive component region, below the protective diode 22provided between the gate G and the drain D.

The thickness of the first insulating film 12 can be changed to adjustthe capacitance of the capacitor C45, which has the first insulatingfilm 12 as the capacitive component region, to necessary staticelectricity resistance. For example, when the protective diode 22 has anelectrostatic breakdown voltage of about 200 V, a capacitance of about90 pF is required. Therefore, the thickness of the first insulating film12 may be equal to or greater than the thickness of the gate insulatingfilm 32 and equal to or less than 1000 Å.

As described above, according to Embodiment 10, the capacitive componentregion is formed between the semiconductor substrate 100, which isarranged below the protective diode 22 provided between the gate G andthe drain D, and the protective diode 22. Therefore, it is possible toimprove the static electricity resistance of the protective diode 22,without increasing the area of the protective diode 22.

Embodiment 11

A semiconductor device according to Embodiment 11 of the invention willbe described. FIG. 17 is a cross-sectional view illustrating thestructure of the semiconductor device according to Embodiment 11 of theinvention. The planar structure of the semiconductor device according toEmbodiment 11 is the same as the planar structure in Embodiment 1illustrated in FIG. 1. FIG. 17 illustrates the cross-sectional structureof the semiconductor device according to Embodiment 11 taken along thecutting line B-B′ of FIG. 1. The semiconductor device according toEmbodiment 11 is a modification of the semiconductor device according toEmbodiment 8. The semiconductor device according to Embodiment 11differs from the semiconductor device according to Embodiment 8 in thata portion of an interlayer insulating film 17 interposed between a firstsemiconductor layer 15 and a second semiconductor layer 16 is acapacitive component region.

As illustrated in FIG. 17, the gap between the first semiconductor layer15 below an anode metal wiring line 6 and the second semiconductor layer16 below a cathode metal wiring line 7 is narrowed to form a capacitorC46 which has the interlayer insulating film 17 provided between thefirst semiconductor layer 15 and the second semiconductor layer 16 asthe capacitive component region. The gap between the first semiconductorlayer 15 and the second semiconductor layer 16 may be, for example,about 0.5

As described above, according to Embodiment 11, it is possible to form acapacitive component region below the anode metal wiring line 6 and thecathode metal wiring line 7 which are provided from a temperaturedetecting diode 1 to an anode electrode pad 3 and a cathode electrodepad 4, without reducing the area of an active region 8. Therefore, it ispossible to improve the static electricity resistance of the temperaturedetecting diode 1.

Embodiment 12

A method for producing a semiconductor device according to Embodiment 12of the invention will be described. FIG. 18 is a cross-sectional viewillustrating the method for producing the semiconductor device accordingto Embodiment 12 of the invention. A method for producing the protectivediode 21 between the gate G and the source S according to Embodiment 3will be described as an example of Embodiment 12.

First, as illustrated in FIG. 18(A), the trench 31 is formed in thesemiconductor substrate 100, in which the first semiconductor region 10is formed in the surface layer of the first semiconductor layer 9 bydiffusion, so as to extend from the first main surface of thesemiconductor substrate 100 to the first semiconductor layer 9 throughthe first semiconductor region 10. Then, the first insulating film 12 isformed on the surface of the semiconductor substrate 100 (the first mainsurface of the semiconductor substrate 100 and the inner wall of thetrench 31) by thermal oxidation. The first insulating film 12 which isformed along the inner wall of the trench 31 is the gate insulating film32. That is, the first insulating film 12 is formed in the same step asthe gate insulating film 32.

Then, polysilicon for forming the conductive layer 14 is deposited onthe first insulating film 12 by a chemical vapor deposition (CVD) methodwhile being doped with n-type impurities. The impurity concentration ofthe conductive layer 14 is in the range of, for example, 4×10²⁰ cm⁻³ to5×10²⁰ cm⁻³. In this case, the conductive layer 14 provided in thetrench 31 is the gate electrode 33. That is, the conductive layer 14 isformed in the same step as polysilicon for forming the gate electrode 33is deposited.

Then, as illustrated in FIG. 18(B), the conductive layer 14 is patternedand the gate electrode 33 is formed in the trench 31. In addition, theconductive layer 14 is formed on the first insulating film 12. In thiscase, the thickness of the conductive layer 14 is, for example, 0.5

Then, as illustrated in FIG. 18(C), the second insulating film 13 isformed with a thickness that is equal to or greater than the thicknessof the gate insulating film 32 on the entire surface of the conductivelayer 14 by thermal oxidation or the CVD method. The thickness of thesecond insulating film 13 may be equal to or greater than the thicknessof the gate insulating film 32 and equal to or less than 1000 Å. Then, asemiconductor layer 18 which is made of undoped polysilicon for formingthe protective diode 21 is formed with a thickness of, for example, 0.5μm to 1 μm on the second insulating film 13 by the CVD method and isthen patterned.

Then, as illustrated in FIG. 18(D), p-type impurity ions and n-typeimpurity ions are selectively implanted into the semiconductor layer 18in this order and an activation process is performed to form theprotective diode 21 including the p⁺ layer 111 and the n⁺ layer 112. Thep-type impurity ions and the n-type impurity ions are sequentiallyimplanted using a mask obtained by patterning a resist (not illustrated)formed on the semiconductor layer 18 in a predetermined pattern. At thesame time as the n-type impurity ions are implanted, the n-type impurityions are implanted into the first semiconductor region 10 in the activeregion 8 to form the second semiconductor region 11 in the surface layerof the first semiconductor region 10.

In the implantation of the n-type ions, for example, arsenic is used asa dopant and impurity concentration is in the range of, for example,about 0.5×10²⁰ cm⁻³ to 2.5×10²⁰ cm⁻³. In the implantation of the p-typeions, for example, boron is used as the dopant and impurityconcentration is in the range of, for example, about 0.5×10²⁰ cm⁻³ to2.5×10²⁰ cm⁻³. The impurity concentration of the second semiconductorregion 11 is in the range of, for example, about 0.5×10²⁰ cm⁻³ to2.5×10²⁰ cm⁻³ and, for example, arsenic is used as the dopant.

In addition, phosphorus may be used instead of arsenic which isimplanted in the ion implantation. Then, as illustrated in FIG. 18(E),the interlayer insulating film 17 is formed on the first main surface ofthe semiconductor substrate 100 and is then patterned. In this case, theconductive layer 14 is electrically insulated from the gate electrode 33or each electrode which is formed in the subsequent steps by theinterlayer insulating film 17 and the second insulating film 13. Then,the other element structures are formed on the first main surface sideof the semiconductor substrate 100 by a general method and a drainregion or a drain electrode is formed on the second main surface side ofthe semiconductor substrate 100. In this way, the semiconductor deviceillustrated in FIG. 5 is completed.

As an example of the method for producing the semiconductor deviceaccording to Embodiment 12, a method for producing the protective diode21 has been described. However, the invention can also be applied to amethod for producing the temperature detecting diode 1 and a method forproducing the protective diode 22 between the gate G and the drain D.

As described above, according to Embodiment 12, the first insulatingfilm 12 is used as the gate insulating film 32 and polysilicon forforming the gate electrode 33 is used as the conductive layer 14.Therefore, it is possible to reduce the number of production steps.

Embodiment 13

FIG. 19 is a cross-sectional view illustrating a method for producing asemiconductor device according to Embodiment 13 of the invention. Amethod for producing a portion below the anode metal wiring line 6 andthe cathode metal wiring line 7 which connect the temperature detectingdiode 1 and the anode and cathode electrode pads 3 and 4 in Embodiment 2will be described as an example of Embodiment 13.

First, as illustrated in FIG. 19(A), the trench 31 is formed in thesemiconductor substrate 100, in which the first semiconductor region 10is formed in the surface layer of the first semiconductor layer 9 bydiffusion, so as to extend from the first main surface of thesemiconductor substrate 100 to the first semiconductor layer 9 throughthe first semiconductor region 10. Then, the first insulating film 12 isformed on the surface of the semiconductor substrate 100 (the first mainsurface of the semiconductor substrate 100 and the inner wall of thetrench 31) by thermal oxidation. The first insulating film 12 which isformed along the inner wall of the trench 31 is the gate insulating film32. That is, the first insulating film 12 is formed in the same step asthe gate insulating film 32.

Then, polysilicon for forming the conductive layer 14 is deposited onthe first insulating film 12 by a CVD method while being doped withn-type impurities. The impurity concentration of the conductive layer 14is in the range of, for example, 4×10²⁰ cm⁻³ to 5×10²⁰ cm⁻³. In thiscase, the conductive layer 14 provided in the trench 31 is the gateelectrode 33. That is, the conductive layer 14 is formed in the samestep as polysilicon for forming the gate electrode 33 is deposited.

Then, as illustrated in FIG. 19(B), the conductive layer 14 is patternedand the gate electrode 33 is formed in the trench 31. In addition, theconductive layer 14 is formed on the first insulating film 12. In thiscase, the thickness of the conductive layer 14 is in the range of, forexample, 0.5 μm to 1 μm.

Then, as illustrated in FIG. 19(C), the second insulating film 13 isformed with a thickness that is equal to or greater than the thicknessof the gate insulating film 32 on the entire surface of the conductivelayer 14 by thermal oxidation or the CVD method. The thickness of thesecond insulating film 13 may be equal to or greater than the thicknessof the gate insulating film 32 and equal to or less than 1000 Å. Then, asemiconductor layer 18 which is made of undoped polysilicon for formingthe first semiconductor layer 15 and the second semiconductor layer 16is formed on the second insulating film 13 by the CVD method and is thenpatterned. The thickness of the first semiconductor layer 15 and thesecond semiconductor layer 16 is in the range of, for example, 0.5 μm to1 μm.

In addition, p-type impurity ions and n-type impurity ions areselectively implanted into the semiconductor layer in this order and anactivation process is performed such that the first semiconductor layer15 and the second semiconductor layer 16 have predetermined conductivitytypes. The p-type impurity ions and the n-type impurity ions for formingthe first semiconductor layer 15 and the second semiconductor layer 16are sequentially implanted using a mask obtained by patterning a resist(not illustrated) formed on the undoped semiconductor layer in apredetermined pattern. At the same time as the n-type impurity ions areimplanted, the n-type impurity ions are implanted into the firstsemiconductor region 10 in the active region 8 to form the secondsemiconductor region 11 in the surface layer of the first semiconductorregion 10.

In the implantation of the n-type ions, for example, arsenic is used asa dopant and impurity concentration is in the range of, for example,about 0.5×10²⁰ cm⁻³ to 2.5×10²⁰ cm⁻³. In the implantation of the p-typeions, for example, boron is used as the dopant and impurityconcentration is in the range of, for example, about 0.5×10²⁰ cm⁻³ to2.5×10²⁰ cm⁻³.

In addition, phosphorus may be used instead of arsenic which isimplanted in the ion implantation. Then, as illustrated in FIG. 19(D),the interlayer insulating film 17 is formed on the first main surface ofthe semiconductor substrate 100 and is then patterned. In this case, theconductive layer 14 is electrically insulated from the gate electrode 33or each electrode which is formed in the subsequent steps by theinterlayer insulating film 17 and the second insulating film. Then, theother element structures are formed on the first main surface side ofthe semiconductor substrate 100 by a general method and a drain regionor a drain electrode is formed on the second main surface side of thesemiconductor substrate 100. In this way, the semiconductor deviceillustrated in FIG. 4 is completed.

The first semiconductor layer 15 below the anode metal wiring line 6 andthe second semiconductor layer 16 below the cathode metal wiring line 7are formed at the same time as the temperature detecting diode 1.Therefore, the first insulating film 12, the conductive layer 14, andthe second insulating film 13 below the anode metal wiring line 6 andthe cathode metal wiring line 7 are each formed at the same time as thefirst insulating film 12, the conductive layer 14, and the secondinsulating film 13 in the step of forming the temperature detectingdiode 1. The semiconductor layer which is made of undoped polysiliconfor forming the first semiconductor layer 15 and the secondsemiconductor layer 16 is formed at the same time as the semiconductorlayer which is made of undoped polysilicon for forming the temperaturedetecting diode 1.

As described above, according to Embodiment 13, the first insulatingfilm 12 is used as the gate insulating film 32 and polysilicon forforming the gate electrode 33 is used as the conductive layer 14.Therefore, it is possible to reduce the number of production steps.

When the method for producing the semiconductor device according toEmbodiment 13 is applied to Embodiments 8 to 11, the step of forming theconductive layer 14 and the second insulating film 13 may be omitted. Inthis case, a capacitive component region is formed between thetemperature detecting diode 1 and the semiconductor substrate 100,between the protective diodes 21 and 22 and the semiconductor substrate100, between the semiconductor substrate 100 and the first semiconductorlayer 15 below the anode metal wiring line 6, or between thesemiconductor substrate 100 and the second semiconductor layer 16 belowthe cathode metal wiring line 7.

When the method for producing the semiconductor device according toEmbodiment 13 is applied to Embodiments 1 to 7, a capacitive componentregion is formed between the temperature detecting diode 1 and theconductive layer 14, between the protective diodes 21 and 22 and theconductive layer 14, between the conductive layer 14 and the firstsemiconductor layer 15 below the anode metal wiring line 6, and betweenthe conductive layer 14 and the second semiconductor layer 16 below thecathode metal wiring line 7. In addition, a capacitive component regioncan be formed between the conductive layer 14 and the semiconductorsubstrate 100. Therefore, it is possible to improve the staticelectricity resistance of the temperature detecting diode 1 and theprotective diodes 21 and 22, as compared to Embodiments 8 to 11. Iaddition, since the conductive layer 14 is electrically insulated fromthe gate electrode 33, the source electrode 34, the drain electrode 35,the anode electrode, and the cathode electrode, it is possible toprevent the adverse effect of a surge voltage applied to each electrode.

The invention is not limited to the above-described embodiments, butvarious modifications and changes of the invention can be made withoutdeparting from the scope and spirit of the invention. In addition, ineach embodiment, the first conductivity type is an n type and the secondconductivity type is a p type. However, the invention is not limitedthereto. The first conductivity type may be a p type and the secondconductivity type may be an n type. In this case, the same effect asdescribed above is obtained.

INDUSTRIAL APPLICABILITY

As described above, the semiconductor devices and the semiconductordevices production methods according to the invention are useful for MOSsemiconductor elements including a temperature detecting diode or aprotective diode.

EXPLANATIONS OF LETTERS OR NUMERALS

-   -   1 TEMPERATURE DETECTING DIODE    -   2 PROTECTIVE DIODE    -   3 ANODE ELECTRODE PAD    -   4 CATHODE ELECTRODE PAD    -   5 GATE ELECTRODE PAD    -   6 ANODE METAL WIRING LINE    -   7 CATHODE METAL WIRING LINE    -   8 ACTIVE REGION    -   9 FIRST SEMICONDUCTOR LAYER    -   10 FIRST SEMICONDUCTOR REGION    -   11 SECOND SEMICONDUCTOR REGION (SOURCE REGION)    -   12 FIRST INSULATING FILM    -   13 SECOND INSULATING FILM    -   14, 14 a, 14 b CONDUCTIVE LAYER    -   15 FIRST SEMICONDUCTOR LAYER    -   16 SECOND SEMICONDUCTOR LAYER    -   17 INTERLAYER INSULATING FILM    -   18 SEMICONDUCTOR LAYER    -   19 INSULATING FILM    -   21 PROTECTIVE DIODE BETWEEN GATE AND SOURCE    -   22 PROTECTIVE DIODE BETWEEN GATE AND DRAIN    -   31 TRENCH    -   32 GATE INSULATING FILM    -   33 GATE ELECTRODE    -   34 SOURCE ELECTRODE    -   35 DRAIN ELECTRODE    -   36 DRAIN REGION    -   37 DRAIN ELECTRODE (SECOND MAIN SURFACE)    -   38 DRAIN REGION (SECOND MAIN SURFACE)    -   51 MOSFET    -   100 SEMICONDUCTOR SUBSTRATE    -   111 p⁺ LAYER    -   112 n⁺ LAYER    -   G GATE    -   S SOURCE    -   D DRAIN    -   A ANODE    -   K CATHODE    -   C1, C1 a, C1 b, C1 c, C1 d, C1 e, C2, C2 a, C2 b, C2 c, C2 d, C2        e, C2 f, C2 g, C2 h, C2 i, C2 j, C3, C3 a, C3 b, C4, C5, C6, C7,        C7 a, C7 b, C7 c, C7 d, C7 e, C8, C9, C9 a, C9 b, C9 c, C9 d, C9        e, C10, C11, C12, C13, C14, C41, C41 a, C41 b, C41 c, C41 d, C41        e, C41 f, C41 g, C41 h, C41 i, C41 j, C42, C43, C44, C44 a, C44        b, C44 c, C44 d, C44 e, C45, C45 a, C45 b, C45 c, C45 d, C45 e,        C46 CAPACITOR

What is claimed is:
 1. A semiconductor device comprising: an insulatedgate semiconductor element that makes a current flow in a thicknessdirection of a semiconductor substrate; a diode that is connected to theinsulated gate semiconductor element; a first insulating film that isformed on a first main surface of the semiconductor substrate and has athickness which is equal to or greater than a thickness of a gateinsulating film of the insulated gate semiconductor element and equal toor less than 1000 Å; a first-conductivity-type layer and asecond-conductivity-type layer that are formed on the first insulatingfilm and form the diode; a first capacitor that has the first insulatingfilm between the first-conductivity-type layer and the semiconductorsubstrate as a first capacitive component region; and a second capacitorthat has the first insulating film between the second-conductivity-typelayer and the semiconductor substrate as a second capacitive componentregion.
 2. The semiconductor device according to claim 1, wherein theinsulated gate semiconductor element includes: a first semiconductorlayer of a first conductivity type that is formed in a surface layer ofthe first main surface of the semiconductor substrate; a firstsemiconductor region of a second conductivity type that is selectivelyformed in a surface layer of the first semiconductor layer which isclose to the first main surface; a second semiconductor region of thefirst conductivity type that is selectively formed in a surface layer ofthe first semiconductor region; and a gate electrode that is formed on asurface of the first semiconductor region, with the gate insulating filminterposed therebetween, in a portion which is interposed between thefirst semiconductor layer and the second semiconductor region.
 3. Asemiconductor device comprising: an insulated gate semiconductor elementthat makes a current flow in a thickness direction of a semiconductorsubstrate; a temperature detecting diode that detects a temperature ofthe insulated gate semiconductor element and is provided in an activeregion of the insulated gate semiconductor element; an anode metalwiring line that is provided on a first main surface side of thesemiconductor substrate and is connected to an anode of the temperaturedetecting diode; a cathode metal wiring line that is provided on thefirst main surface side of the semiconductor substrate and is connectedto a cathode of the temperature detecting diode; a first insulating filmthat is formed on a first main surface of the semiconductor substratebetween the anode and cathode metal wiring lines and the semiconductorsubstrate and has a thickness which is equal to or greater than athickness of a gate insulating film of the insulated gate semiconductorelement and equal to or less than 1000 Å; a first semiconductor layerthat is formed between the first insulating film and the anode metalwiring line and is connected to the anode metal wiring line; a secondsemiconductor layer that is formed between the first insulating film andthe cathode metal wiring line and is connected to the cathode metalwiring line; a first capacitor that has the first insulating filmbetween the first semiconductor layer and the semiconductor substrate asa first capacitive component region; and a second capacitor that has thefirst insulating film between the second semiconductor layer and thesemiconductor substrate as a second capacitive component region.
 4. Thesemiconductor device according to claim 3, wherein the insulated gatesemiconductor element includes: a first semiconductor layer of a firstconductivity type that is formed in a surface layer of the first mainsurface of the semiconductor substrate; a first semiconductor region ofa second conductivity type that is selectively formed in a surface layerof the first semiconductor layer which is close to the first mainsurface; a second semiconductor region of the first conductivity typethat is selectively formed in a surface layer of the first semiconductorregion which is close to the first main surface; and a gate electrodethat is formed on a surface of the first semiconductor region, with thegate insulating film interposed therebetween, in a portion which isinterposed between the first semiconductor layer and the secondsemiconductor region.
 5. The semiconductor device according to claim 1,wherein the diode is a temperature detecting diode that is provided inan active region of the insulated gate semiconductor element and detectsa temperature of the insulated gate semiconductor element.
 6. Thesemiconductor device according to claim 2, further comprising: a gateelectrode pad that is connected to the gate electrode; and a sourceelectrode that is connected to the first semiconductor region and thesecond semiconductor region, wherein the diode is a protective diodethat is formed between the gate electrode pad and the source electrode.7. The semiconductor device according to claim 2, further comprising: agate electrode pad that is connected to the gate electrode; a thirdsemiconductor region of the first conductivity type that is selectivelyformed in the surface layer of the first semiconductor layer which isclose to the first main surface; and a drain electrode that is connectedto the third semiconductor region, wherein the diode is a protectivediode that is formed between the gate electrode pad and the drainelectrode.
 8. The semiconductor device according to claim 1, wherein theinsulated gate semiconductor element is a trench-type insulated gatesemiconductor element.